diff options
author | Andrew Morrow <acm@mongodb.com> | 2017-06-19 12:29:52 -0400 |
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committer | Andrew Morrow <acm@mongodb.com> | 2017-07-01 14:32:17 -0400 |
commit | edc858ca3a32974c07f027e6860a52ac6e89039b (patch) | |
tree | 58252193a03b478310b8cc7e27d9b8f80d048cb4 /src/mongo/util | |
parent | be90e394a3a21ad38feed6d132e326bab27de5dd (diff) | |
download | mongo-edc858ca3a32974c07f027e6860a52ac6e89039b.tar.gz |
SERVER-29462 Align locks in mongo::Paritioned to avoid false sharing
Diffstat (limited to 'src/mongo/util')
-rw-r--r-- | src/mongo/util/with_alignment.h | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/src/mongo/util/with_alignment.h b/src/mongo/util/with_alignment.h new file mode 100644 index 00000000000..b1128f527ff --- /dev/null +++ b/src/mongo/util/with_alignment.h @@ -0,0 +1,65 @@ +/** + * Copyright (C) 2017 MongoDB Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU Affero General Public License, version 3, + * as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Affero General Public License for more details. + * + * You should have received a copy of the GNU Affero General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + * As a special exception, the copyright holders give permission to link the + * code of portions of this program with the OpenSSL library under certain + * conditions as described in each individual source file and distribute + * linked combinations including the program with the OpenSSL library. You + * must comply with the GNU Affero General Public License in all respects + * for all of the code used other than as permitted herein. If you modify + * file(s) with this exception, you may extend this exception to your + * version of the file(s), but you are not obligated to do so. If you do not + * wish to do so, delete this exception statement from your version. If you + * delete this exception statement from all source files in the program, + * then also delete it in the license file. + */ + +#pragma once + +#include <algorithm> + +#include "mongo/stdx/new.h" + +namespace mongo { + +/** + * Creates a new type with the same interface as T, but having the + * given alignment. Note that if the given alignment is less than + * alignof(T), the program is ill-formed. To ensure that your program + * is well formed, see WithAligmentAtLeast, which will not reduce + * alignment below the natural alignment of T. + */ +template <typename T, size_t alignment> +struct alignas(alignment) WithAlignment : T { + using T::T; +}; + +/** + * Creates a new type with the same interface as T, but having an + * alignment greater than or equal to the given alignment. To ensure + * that the program remains well formed, the alignment will not be + * reduced below the natural alignment for T. + */ +template <typename T, size_t alignment> +using WithAlignmentAtLeast = WithAlignment<T, std::max(alignof(T), alignment)>; + +/** + * Creates a new type with the same interface as T but guaranteed to + * be aligned to at least the size of a cache line. + */ +template <typename T> +using CacheAligned = WithAlignmentAtLeast<T, stdx::hardware_destructive_interference_size>; + +} // namespace mongo |